Sievert vs Gray

[robryk]

rink currently does:

> 1 Sv
1 gray (specific_energy)

which is incorrect and arguably misleading.

Background on absorbed vs equivalent dose

Gray is a unit of absorbed radiation dose, with a somewhat abstruse meaning of dose -- it would make more sense to call it dose density. Sievert is a unit of biological effects caused by absorbed radiation ("equivalent dose"). It's also defined as J/kg, but 1 Sv really means something like "a dose of some radiation that would have equivalent effect to 1 Gy of Gamma radiation at <some standard wavelength>". Strictly speaking, converting between the two is impossible: the equivalent dose corresponding to a particular absorbed dose depends on what radiation was used.

What we can do?

• nothing, because the conversion we're implying is roughly appropriate for Gamma, which this is most likely to be used for,
• act contrary to SI definitions and claim that Sievert is a base unit (which IMO is most consistent with how they are to be used),
• define Sv to be J/kg*some_unit -- effectively claim, contrary to SI definitions, that the quality factor has a unit,
• something else?

[tiffany352]

The current version of rink, 0.8.0, doesn't use gray for finding units anymore. Instead, it displays as 1 meter^2 / second^2 (specific_energy). (See #13)

I might add a special case to display this as 1 J/kg instead, which is more intuitive. It's annoying that SI doesn't have a derived unit for this that's actually general purpose.